The London Mayor is supporting the Takeaways Toolkit, guidance published by the London Food Board in partnership with the Chartered Institute of Environmental Health.

The guide will be issued to London councils this week and includes a raft of suggestions for encouraging healthy eating, from restricting takeaway sites with tighter planning guidelines to introducing healthy “grab and go” options in schools.

Twenty of the capital’s boroughs have a concentration of fast-food outlets that is well above the national average.

Mr Johnson said: “As a city, as a nation, we are getting fatter. Just over a third of 10 and 11-year-olds are overweight or obese, with numbers rising all the time, contributing to a problem that costs the NHS as much as £4 billion annually.

“This guide shows how councils can manage the proliferation of takeaways across the capital, but also how by working with businesses as well as schools, we can all be served up much healthier tucker.”

There are an estimated 8,273 fast-food takeaway shops in London, one for every 1,000 Londoners.

Seven of the 10 London boroughs with the highest concentration of fast-food takeaways are also in the top 10 for deprivation, according to analysis by Greater London Authority.

The new guidelines provide local authorities with a variety of ideas to help tackle that problem.

One suggestion is for councils to work directly with takeaway owners to cut saturated fats, salt and sugar in their cooking and introduce low-fat foods to the menu.

For example, one London takeaway dramatically cut levels of saturated fat on chips after switching from palm oil to rapeseed oil on the advice of an environment health officer.

Local authorities are similarly advised on how to use planning guidelines to restrict where and when takeaways set up, as well as how to use environmental and health regulations and laws around street trading.

Mr Johnson’s new push to tackle London’s obesity problem follows measures implemented across the Atlantic by New York mayor Michael Bloomberg, who has banned extra large cups of sugary drinks.

In June, Mr Johnson responded to Mr Bloomberg’s idea by writing that “where New York leads, London is not far behind”.

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